Bimetallic Cr-In/H-SSZ-13 for selective catalytic reduction of nitric oxide by methane  

双金属Cr-In/H-SSZ-13催化剂上CH_4选择催化还原NO（英文）

作　　者：Jun Yang Yupeng Chang Weili Dai Guangjun Wu Naijia Guan Landong Li 杨俊;常煜鹏;戴卫理;武光军;关乃佳;李兰冬(南开大学材料科学与工程学院,国家新材料研究院,天津300350;南开大学先进能源材料化学教育部重点实验室,化学化工协同创新中心,天津300071)

机构地区：[1]School of Materials Science and Engineering&National Institute for Advanced Materials,Nankai University,Tianjin 300071,China [2]Key Laboratory of Advanced Energy Materials Chemistry of the Ministry of Education,Collaborative Innovation Center of Chemical Science and Engineering,Nankai University,Tianjin 300071,China

出　　处：《Chinese Journal of Catalysis》2018年第5期1004-1011,共8页催化学报（英文）

基　　金：国家自然科学基金(21773127,21722303,21421001);高等学校学科创新引智计划(111计划,B18030).

摘　　要：Bimetallic Cr-In/H-SSZ-13 zeolites were prepared by wet impregnation and investigated for selective catalytic reduction of nitric oxide by methane(CH4-SCR).Reduction-oxidation treatments led to close contact and interaction between Cr and In species in these zeolites,as revealed by transmission electron microscopy and X-ray photoelectron spectroscopy.Compared to monometallic Cr/H-SSZ-13 and In/H-SSZ-13,the bimetallic catalyst system exhibited dramatically enhanced CH4-SCR performance,i.e.,NO conversion greater than 90%and N2 selectivity greater than 99%at 550°C in the presence of 6%H2O under a high gas hourly space velocity of 75 000/h.The bimetallic Cr-In/H-SSZ-13 showed very good stability in CH4-SCR with no significant activity loss for over 160 h.Catalytic data revealed that CH4 and NO were activated on the In and Cr sites of Cr-In/H-SSZ-13,respectively,both in the presence of O2 during CH4-SCR.天然气(主要成分为甲烷)储量丰富,价格低,随着国内电厂煤改气的进行,甲烷作为还原剂选择催化还原氮氧化物成为电厂烟气脱硝的理想选择,受到广泛关注.In改性分子筛催化剂在甲烷选择催化还原一氧化氮反应(CH_4-SCR)中表现出一定催化性能,而In基双金属被认为是最有前景的CH_4-SCR催化剂.本文通过湿浸渍法制备了分子筛双金属催化剂,并成功应用于CH_4-SCR.我们首先研究了不同分子筛载体、助剂及含量、氧气浓度、甲烷浓度和空速对反应的影响,发现0.5%Cr-2%In/H-SSZ-13在CH_4-SCR中表现出最佳的催化性能:NO转化率>90%,N_2选择性>99%(反应条件:550°C,6%H_2O,空速75 000/h).从透射电镜照片可以看出,0.5%Cr-2%In/H-SSZ-13催化剂上均匀分布纳米尺寸颗粒,扫描透射-高角环形暗场像元素分布分析表明Cr与In出现在同一个位置,即Cr与In紧密接触.X射线光电子能谱结果表明,与单金属催化剂相比,双金属催化剂中In的能谱发生了明显偏移,Cr与In存在电子相互作用.CH_4-SCR反应活性实验发现,双金属催化剂活性远远超过单金属催化剂活性及其机械混合物,表明Cr的添加可以明显促进In的活性.换言之,双金属催化剂中,Cr与In存在协同催化作用.Cr-In/H-SSZ-13在严苛反应条件下的活性长期保持不变,具有良好稳定性,这与沸石分子筛载体H-SSZ-13的高热稳定性分不开.结合稳态反应与程序升温表面反应结果,可以推测有氧条件下CH_4和NO分别在In和Cr位点上活化.

关 键 词：Selective catalytic reduction Nitric oxide METHANE Cr-In/H-SSZ-13 Bimetallic catalyst 

分 类 号：O643.32[理学—物理化学]